Impact: Most residents of the New Orleans area - perhaps more than a million - left before the hurricane hit. Behind them, their city was wrecked and tens of thousands of survivors who had not joined the exodus were trapped. Sitting below sea level, in a bowl surrounded by the sea, a lake and the Mississippi River, New Orleans is highly vulnerable to flooding. In the days after the storm hit, almost the whole city was submerged. Buildings and roads have been swept away, power and water cut off, and hospitals isolated.

Toll:
New Orleans Mayor Ray Nagin has said a figure of 10,000 deaths "wouldn't be unreasonable". A definitive death count has been impossible while parts of the city remain unreachable.

Conditions: With the evacuation of thousands of survivors, New Orleans is left resembling a ghost town. Rescue teams continue to search for survivors, but recovery of bodies has also begun. Homeland Security Secretary Michael Chertoff says any number of people could still be found dead in swamped homes and shelters. Police officers are urging people who have chosen to remain in their homes to leave because the city is uninhabitable. Engineers have repaired a breach in the 17th Street Canal floodwall and started pumping water, but large swathes of the city remain submerged. In other areas where floodwater has receded, streets are deserted.

"The city has no clean water, no sewage system, no electricity, and no real communications. Bodies are still being recovered, found floating in the floods. We are worried about a cholera epidemic. Even the police are without effective communications," New Orleans resident Greg Henderson told the BBC.

Impact:
The resort town of 50,000 people was smashed by the storm. People's homes, clothes, food and cars were swept away by a 30ft (9m) surge of floodwater. The seafront casinos that fuelled the local economy have been destroyed.

Toll: It is estimated more than 100 people died in Harrison County, which includes Biloxi and Gulfport.

Conditions: Most of Biloxi remains without water or power. Lorries loaded with food, water and ice are arriving but distribution has been slow and unreliable. Officials have warned of the risk of disease from contaminated water. Some people remain in their wrecked homes but say they need federal aid if they are to start rebuilding. Many are in emergency shelters or hotels. The authorities say they will eventually offer temporary housing in tents or trailers. Thousands of engineers are working to restore power, which the Mississippi Power Company says could take up to four weeks.

K Gordon from near Biloxi told the BBC: "Pascagoula, Gautier, Biloxi, Pass Christian, D'Iberville - places where I lived, my friends are at, my family. They are practically destroyed. The Vietnamese district in Biloxi is basically under water. I have sick family members that I can't get to. My home and the homes of everyone I love are gone. What am I supposed to do?"

Impact: The town was battered by 135mph (217 km/h) winds that tossed many of the city's casino barges onto the shore. Most buildings suffered roof damage, and many were completely destroyed.

Toll: It is estimated more than 100 people died in Harrison County, which includes Biloxi and Gulfport.

Conditions: Electricity is down, so there is no refrigeration, no pumped petrol, no light or air conditioning. Disease warnings have been issued, with clean water in short supply. Security has now been restored after incidents of looting and lawlessness. Reports from towns to the west of Gulfport say that local people have been moving bodies themselves from wreckage or from waterways.

Mallory Whitfield from Gulfport e-mailed the BBC to say: "Our back porch roof was ripped off completely [but] we count ourselves lucky, the house is still liveable and everyone who stayed there is safe. My mother's business and entire source of income, however, is completely destroyed. All of my friends from New Orleans have given up hope of salvaging their homes and possessions."

Impact: Many homes and vehicles were flooded, and power was cut off to 325,000 homes and businesses.

Toll: Two deaths have been reported.

Conditions: Queues, hundreds of cars long, have formed at petrol stations, and food, ice and water are being handed out.
On Thursday the port was re-opened, allowing crops to be exported, and a major bridge was reopened after being struck by a drifting oil drilling platform.

Robert Barnett e-mailed the BBC News website from Mobile to say: "Here in Mobile, it's bad, very bad.
Thousands without power, people fighting for petrol, literally. We did not fare as badly as Gulfport, Biloxi or New Orleans, but there are towns totally obliterated, gone."